Using lube while seating bullets

Was doing some reloadin gprocess review the other day and started thinkng about placing a smear of Imperial case sizing wax on the bullet or case mouth when seating. Noticed that Glen Zedicker (sp) suggested this in his book.

What are the facts about this practice vs leaving the inside of the case and bullet unlubed? What are your processes and what have you seen as far as results before and after?